Method of making split metal packing rings

ABSTRACT

A circular ring blank is strained to impart radial springiness or resiliency thereto by way of a reduction (compression) of the opposite outer flat surfaces thereof on the sections adjacent to the cylindrical surface opposite to its cylindrical sealing surface. Maximum reduction force is applied to the outer flat surfaces that lie against the split and as far as half the width of the ring width, with the same being gradually decreased to zero on the outer flat surfaces adjacent to the ring split.

United States Patent [191 Zabolotsky et al.

[ METHOD OF MAKING SPLIT METAL PACKING RINGS [76] Inventors: GrigoryMikhailovich Zabolotsky,

[22] Filed: Nov. 3, 1971 [21] Appl. No.: 195,190

[52] U.S. Cl. 29/l56.6

[51] Int. Cl B23p 15/06 [58] Field of Search 29/l56.6; 72/340; 277/216,277/217, 225

[56] References Cited UNITED STATES PATENTS 2,591,920 4/1952 Colvin277/216 Karamyshevdksya naberezhnaya, 24, kv. 27; Vladimir MikhailovichRakovsky, Ulitsa petrozavodskaya,

l5, Korpus 1, kv. 65, both of Moscow; Sergei Alexandrovich Shuster,Krasnogorodsky raion, poselok Opalikha, ulitsa Leninskaya, l3, kv. 5,Moskovskaya Oblast; Mikhail Vsevolodovich Boldyrev, Ulitsa putevoiproezd, 38,

kv. 77, Moscow, all of U;S.S.R.

[ May 21, 1974 Wenzel 277/216 Schimdt.... 277/216 Petter 29/l56 6Koehler 29/156.6 Farr 277/216 Primary Examiner-Charles W. LanhamAssistant ExaminerM. J. Keenan Attorney, Agent, or Firm-Holman & SternABSTRACT A circular ring blank is strained to impart radial springinessor resiliency thereto by way of a reduction (compression) of theopposite outer flat surfaces thereof on the sections adjacent to thecylindrical surface opposite to its cylindrical sealing surface. Maximumreduction force is applied to the outer flat surfaces that lie againstthe split and as far as half the width of the ring width, with the samebeing gradually decreased to zero on the outer flat surfaces adjacent tothe ring split.

2 Claims, 15 Drawing Figures PATENTED MAY 21 I974 SHEET 2 BF 2 FIG. 1/

FIG.

METHOD OF MAKING SPLIT METAL PACKING RINGS BACKGROUND OF THE INVENTIONThe present invention relates generally to plastic metal workingpractice and more specifically, to a method of making split metalpacking rings.

The present method is instrumental in making packing rings, in whichsealing surfaces are in fact the outside cylindrical surface and facesurfaces (the so-called outside-pressure rings, i.e., piston rings), aswell as packing rings, in which the sealing surfaces are, in effect, theinside cylindrical surface and face surfaces. Unlike pistons these willhereinafter be referred to as inside-pressure rings.

PRIOR ART All the heretofore-known methods of making split metal packingrings differ in the principle underlying the ring-shaping process, i.e.,the rings, when free, have imparted thereto such an out-of-round shapethat when fitted into a cylinder (in case of packing rings) or fittedonto the piston rod or a sphere (in case of insidepressure rings), theywould have a circular shape and exert largely a uniform pressure uponthe adjacent surface of the part being packed (cylinder or piston rod)throughout its periphery.

Known in the art is a method of making split metal inside-pressurepacking rings, in which a circular turned ring blank has impartedthereto the desired elastic properties to suit the requirement ofexerting a uniform inside pressure by the ring when in its workingposition, due to straining said ring blank in a radial direction byradial indents or notches made on the outside cylindrical surface of thering blank with a presetshaped driftpin. The indents or notches resultfrom strikes delivered against the outside cylindrical surface of thering blank at the same force but spaced apart from one anothercircumferentially at an everincreasing distance (at variable pitch) sothat the minimum notch spacing is given to the surface lying against thering split and the maximum spacing, to the surface adjacent to thesplit. Notches can be made on the outside cylindrical surface of thering blank at a regular pitch as well, but by gradually increasing thestriking force and, consequently, the notching depth so that the maximumforce is applied to the ring surface located against the split and theminimum force, to that adjacent to the ring split.

A disadvantage inherent in said method is that it is highly laboriousand, consequently, a low-efficiency method since 120 to 180 notches ofdifferent depths or pitches are to be made on the outside cylindricalsurface of a ring blank in order to strain it by the above mentionedmethod.

Besides, there is known to be in widespread use, a method of makingpiston rings, in which the required out-of-round shape of the ring whenin free state is obtained by casting a non-round ring blank followed bya mechanical treatment of said blank to a former or templet.

The method, however, suffers likewise from complexity and high laborconsumption of the production process, since it requires an individualcasting of every ring blank and subsequent milling of avariablecurvature ring to a former or templet.

OBJECTS AND SUMMARY OF THE INVENTION 1 It is an object of the presentinvention to provide a simpler and less laborious method ofmakingpacking rings.

It is another object of the present invention to provide a method ofmaking packing rings which is highly efficient.

According to the above and other objects, provision is made for a methodof making packing rings, in which a circular ring blank is strained toimpart radial elastic properties (springiness) thereto, whereupon saidring is subject to a consecutive machining on the face, the outsidecylindrical and inside cylindrical surfaces thereof, and in which,according to the invention the ring blank is strained by reduction ofthe opposite outer flat surfaces thereof on the sections adjacent to itsoutside cylindrical surface lying opposite to the ring cylindricalsealing surface; maximum reduction force is applied to the outer flatsurfaces lying against the split of the ring blank as far as half thewidth of the ring and is gradually decreased to a minimum when appliedto the outer flat surfaces close to the split of the ring blank.

It is expedient, when making packing rings, in which the outsidecylindrical surface serves as a sealing surface, to reduce the sectionsof the opposite outer flat surfaces of the ring blank which are adjacentto the inside cylindrical surface thereof.

Reduction of such a section of the outer flat surface of the ring blankis used when making piston rings.

It is likewise practicable, when making packing rings, in which theinside cylindrical surface serves as a sealing surface, to reduce thesections of the ring blank end faces which are adjacent to the outsidecylindrical surface thereof.

Reduction of such a section of the outer flat surface of the ring blankis used when making inside-pressure rings.

The present method of making split metal packing rings, though simpleand non-laborious, renders high production capacity and good quality ofthe packing rings produced.

Given below is a description of specific embodiments of the presentinvention with due reference to the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows an inside-pressure packingring while in a working position;

FIG. 2 is a view partly in elevation and partly in cross section of areducing die with plane working surfaces which embodies a method ofmaking split insidepressure packing rings, according to the inventionand a ring blank placed therein;

FIG. 3 is a view taken along line III-Ill in FIG. 1, the view looking inthe direction of the arrows;

FIG. 4 is a side view of an inside-pressure packing ring while in aninoperative position;

FIG. 5 shows a piston ring while in a working position;

FIG. 6 is a fragmentary view partly in elevation and partly in crosssection of a reducing die with plane working surfaces which embodies amethod of making piston rings, according to the invention and a ringblank placed therein;

FIG. 7 is a view taken along line VII-VII in FIG. 5, the view looking inthe direction of the arrows;

FIG. 8 is a side view of a piston ring while in an inoperative position;

FIG. 9 is a fragmentary view partly in elevation and partly in crosssection of a reducing die having a punch with an inner taper workingsurface, to embody a method of making inside-pressure packing rings,according to the invention and a ring blank placed therein;

FIG. 10 is a view taken along line XX in FIG. 1, the view looking in thedirection of the arrows;

FIG. 11 is a fragmentary view partly in elevation and partly in crosssection of a reducing die, wherein its punch has an outer taper workingsurface, to embody a method of making piston rings, and a ring blankplaced therein;

FIG. 12 is a fragmentary view partly in elevation and partly in crosssection of a reducing die, wherein its punch features an innerplanotaper working surface to make inside-pressure rings;

FIG. 13 is a view illustrating an inner-pressure ring reduced in thedie, while in a working position;

. FIG. 14 is a fragmentary view partly in elevation and partly incrosssection of a reducing die, wherein its punch features an outerplanotaper working surface to make piston rings; and

FIG. 15 is a view illustrating a piston ring reduced in i the die, whilein working position.

DETAILED DESCRIPTION OF THE INVENTION Now referring to the drawings, themethod of making inside-pressure packing rings 1 (FIG. 1), in which theinside cylindrical surface of a diameter d serves as a sealing surface,resides in that to impart to the packing ring a radial springiness and auniform inside pressure, a preliminarily heat-treated circular ringblank 2 (FIG. 2), is placed in a die 3 whose punch 4 and bottom block 5have plane working surfaces, in such a manner that the working surfacesof the bottom block 5 and the punch 4 reduce those sections 6 (FIG. 1)of the opposite outer flat surfaces which lie between the circumferenceof a mean diameter d+t and the circumference of an outside diameter D(i.e., outside cylindrical surface). In FIG. I, section 6 being reducedof one outer flat surface is shown crosshatched. For the sake ofclarity, in the specification only one section will be underconsideration but it should be borne in mind that all discussed hereinholds equally true of the same section lying on the opposite outer flatsurface of the ring blank. Height h of the section 6 being reduced is avariable quantity, viz., its maximum value h should not be more than 1/2and is located on the outer flat surface of the ring 1 lying against thesplit, whereupon said quantity gradually decreases to a minimum value (h=0) effective on the outer flat surface close to the split.

Then, the blank 2 is reduced by the pressing effort transmitted to thepunch 4 through a spherical support 7, the amount a (FIG. 3) of the ringstrain by its thickness b a constant quantity.

In this case, a uniform inside pressure exerted by the packing rings 1while in a working position is ensured due to the fact that the width hof the section 6 of the ring blank 2 being reduced throughout its lengthwhich is determined at any cross-section taken along an are by an angled is of variable character and can be found from the formula:

where b is the thickness of the ring I; a is the strain value (reductiondepth) in thickness b of the ring I;

b/a is a reciprocal of compressive strain;

d is the inside diameter of the ring 1;

t is the width of the ring I;

d t the ring mean diameter.

A is the amount of overlap of the ends of the ring 1 while in a freestate (i.e., inoperative) which depends (with the given values ofthering parameters d, t and 12) upon the preset unit pressure;

4) is an angle (coordinate [1) taken from the ring midpoint (i.e., thepoint opposite to the split) towards the split and variable through 0 to1r (0 to The physical meaning of the straining resides in that in thematerial of the reduced sections 6 of the packing ring there arise extrastresses (as compared to nonreduced sections 8) variable lengthwise ofthe branches of the ring I. (By the branch of the rings 1 is meant thelength from the point lying against the split to the end adjacentthereto). The extra stresses result in variable radial turns of the ring1 branches on which account the ring, when free, assumes the presetout-of-round shape and the ends of the branches thereof becomeoverlapped as is shown in FIG. 4.

In an ideal case, i.e., leaving out of account the actualout-of-straight of the die 3 punch guides, the working surfaces of thepunch 4 and the bottom block 5 are of plane shape variable only to thewidth of the section 6 of the ring 1 being reduced and determined by theformula (I). Thus, e.g., with the compressive strain value a/b 1% 1/100(selected experimentally), the equation (I) for calculating the insideworking edges of the v punch 4 and the bottom block 5 will be:

.iizqsla-auietu 2M1.

The above-given curve for insidepressure rings is in fact acircumference of the diameter D d 2t k and is the diameter of the innearborder line of the reduced section'6 of the ring 1 outer flat surfaceand the inside diameter of the edge of the working surfaces of the punch4 and the bottom block 5. Besides, the center of the circumference isoffset with respect to that of the ring 1 along an axis 9 passingthrough the split of the ring 1, towards said split by an amount ofeccentricity equal to r e unt As a result of a reduction of the section6 in the die 3, there arise stresses in the material of the ring 1 underwhich the ring acquires a radial springiness on the side of the insidediameter d, while due to a variable character of reduction along thering outside periphery, the ring features a uniform compression diagramon the side of the inside diameter thereof.

Upon having been reduced in the die 3, the ring 1 is subjected to aconventionally known mechanical treatment as follows. The ring 1 isground on the outer flat surfaces to a preset size, whereupon a numberof rings 1 in a quantity of 15 to 20 are fitted onto an inside mandrel(not shown), clamped with nuts on the outer flat surfaces and the wholegroup of the rings is ground along the outside diameter D to a presetsize. When, the inside mandrel together with the rings fitted thereon,is inserted into an outside mandrel, in which the rings 1 are broughtinto alignment with respect to the machined outside diameter D, clampedwith the nut of the outside mandrel, whereupon the inside mandrel isremoved and the rings 1 are ground along the inside diameter d. Upongrinding, the inside diameter d of the ring 1 is lapped to a workingsize.

To make split metal packing rings (FIG. 5) featuring a uniform outsidepressure, i.e., packing rings, in which the outside cylindrical surfaceserves as a sealing surface (viz., piston rings), a ring blank 11 (FIG.6) is placed in a die 12 with plane working surfaces to reduce a section13 of the outer flat surface thereof adjacent to the inside cylindricalsurface of diameter d,. The width h of the section 13 being reduced,just as in the case of the rings 1, is a variable quantity, viz., itsmaximum value h should not be more than [/2 and is located on the outerflat surface of the ring lying against the split, said quantity )1 beinggradually decreased to a minimum value (h 0) effective on the outer flatsurface close to the split. The quantity h is found from the sameformula as the quantity h for the inside-pressure rings 1, with the soleexception that the quantity A (denoting the amount of overlap of thering ends with the ring in free state) is substituted for the quantity L(FIG. 8) by which the ends of the ring 10 are set apart when in a freestate (i.e., while the ring 10 is inoperative), said quantity dependingupon the value of the required external pressure.

h, b la 2/31r L/d +t (l cos qb) (Ill) The section 13 being reduced ofthe piston ring 10 is shown crosshatched in FIG. 5.

With a compressive strain equal to a lb 1% 1/100, equation (III) forcalculating the outer working edge of a punch 14 and a bottom block 15of the die 12 will be as follows:

h ZOO/3w L/d l't (l cos 5) iv For the piston rings 10, this curve is infact a circumference having the diameter D1 =d, h mar whose center isoffset with respect to the center of the ring 10 along an axis 16passing through the split of the ring 10 away from said split by anamount of eccentricity equal to Due to such a reduction of the section13 of the ring 10, stresses arise in the material thereof under whichthe ring 10 acquires radial elastic properties on the side of theoutside diameter D When in a working position, the ring 10 features auniform pressure along the outside diameter 0,.

Upon having been reduced, the ring 10 is subject to a heat treatment(thermal fixing), whereupon the ring undergoes consecutive mechanicaltreatment on the outer flat surfaces, and the inside and outsidecylindrical surfaces thereof to a desired size in a way similar to theinside-pressure rings 1.

Reduction of a circular ring blank 17 (FIG. 9) to obtain aninside-pressure ring may also be made in a die 18, whose punch 19 has aninner working surfaces tapered at an apex angle a, while the workingsurface of a bottom block 20 is plane and is square with the cylindricalface of the ring blank 17. The punch 19 and the bottom block 20 are soset that their center is offset relative the center of the ring blank 17by an amount of eccentricity equal to e h /2 towards the ring split asin the case of the inside-pressure ring 1 (FIG. 1).

Width h (FIG. 10) of the section being reduced of the ring blank 17 is avariable quantity, with its maximum value being on the outer flatsurface opposite to the split and the minimum value, close thereto.Besides, the strain value 0 applied to the ring by the thickness b whenreduction is made in the tapered-surface die 18, is likewise a variablequantity.

Reduction of the outer sections of the ring blank 17 occurs in a radialsection and assumes the shape of a triangle having legs h and a itfollows the following law:

Letter symbols in the above formula are the same as in formula (I).

FIG. 11 represents a die 21 for making piston rings. The die has a punch22 provided with inner working surfaces tapered at a taper apex angle04,. The punch 22 and a bottom block 23 are offset with respect to aring blank 24 by an amount of eccentricity e away from the split. a

When calculating a compressive strain of piston rings, use is made offormula (IV) with the sole exception that the overlap quantity A issubstituted for the quantity L denoting the ring end-to-end distancewhen the ring is in a free state. As to other particulars, the reductionprocess is similar to that above described.

It is likewise practicable to effect a reduction of a ring blank 25(FIG. 12) to obtain an inside-pressure ring 26 (FIG. 13) in a die 27(FIG. 12), in which the working surfaces of a punch 28 and a bottomblock 29, with respect to the outer flat surface of the ring blank 25,have a shape planobevelled towards the split of the ring blank 25 andvariable with the thickness thereof by the value a;,/ 2 of thecompressive strain applied thereto. Besides, the maximum value of a /2will occur on that section of the outer flat surface of the ring blank25 which lies opposite to the ring split, while the value will bedecreased to zero close to the split.

The strain value a is found from the formula:

Letter symbols in the above formula as the same as in formula (I).

When reducing the ring blank 25 the reduction width is the samethroughout the perimeter of the ring 26.

The punch 28 and the bottom block 29 are set concentrically with thering blank 25, with section 30 being reduced being shown crosshatched inFIG. 13.

Reduction of a ring blank 32 in a die 31 (FIG. 14) having planobevelledworking surfaces to obtain a piston ring 33 (FIG. 15) is similar to thatabove described. The strain value a., can be obtained from formula (6),with the sole exception being that the ring end overlap value A issubstituted for the ring end setting apart value L.

Upon having been reduced, the rings 26 and 33 assume a rectangular shapein a radial section.

In all of the above-described variants, the variable character of thering blank reduction is ensured due to an appropriate shape of theworking surfaces of the punch and bottom block. The surfaces should bein a strict agreement with each other circumferentially and of fixedquantity, while the minimum zone of reduction of a ring blank (close tothe split) should be marked on the outside of the bottom block with,say, a notch.

With the above-disclosed method of making piston rings whose consumptionin the present day technology may amount to billions, an individualcasting of every ring blank and milling variable-curvature rings to atemplet are completely eliminated which results in a considerablemonetary saving.

A still greater economical effect may be obtained when the presentmethod is used in making insidepressure packing rings as compared to theconventional method of straining a ring blank by the notching method,since the straining process of a ring blank by the present method occursin 1-2 steps of reduction in a die and takes a period of time spentapproximately for making two notches out of ll80 required by the knownmethod, i.e., approximately 6090 times as fast.

the blank material, subjecting said blank to strainingfor impartingelastic properties thereto effective in a radial direction, by reductionof the opposite outer flat surfaces thereof on its sections adjacent tothe outside cylindrical surface of the blank to a value not greater thanhalf of the width of the ring blank in the section diametricallyopposite to the split of the ring blank and compression is graduallydecreased along an arc to a minimum value at the ends of the blank inthe place of the split, and consecutively machining the blank on itsouter flat surfaces and inside and outside cylindrical surfaces to apreset size.

2. A method of making split metal packing rings in which the outsidecylindrical surface serves as a sealing surface, comprising the steps ofstraining a circular ring blank for imparting radial springiness theretoby reduction of the opposite outer flat surfaces thereof on its sectionsadjacent to the inside cylindrical surface of the blank to a value notgreater than half of the width of the ring blank in the sectiondiametrically opposite to the split of the ring blank and compression isgradually decreased along an arc 180 to a minimum value at the ends ofthe blank in the place of the split, heat treating the blank forimparting a homogeneous structure to the material thereof andconsecutively machining the blank on its outer flat surfaces and insideand outside cylindrical surfaces to a preset size.

1. A method of making split metal packing rings in which the insidecylindrical surface serves as a sealing surface, comprising the steps ofheat treating a circular ring blank for imparting a homogeneousstructure to the blank material, subjecting said blank to straining forimparting elastic properties thereto effective in a radial direction, byreduction of the opposite outer flat surfaces thereof on its sectionsadjacent to the outside cylindrical surface of the blank to a value notgreater than half of the width of the ring blank in the sectiondiametrically opposite to the split of the ring blank and compression isgradually decreased along an arc 180* to a minimum value at the ends ofthe blank in the place of the split, and consecutively machining theblank on its outer flat surfaces and inside and outside cylindricalsurfaces to a preset size.
 2. A method of making split metal packingrings in which the outside cylindrical surface serves as a sealingsurface, comprising the steps of straining a circular ring blank forimparting radial springiness thereto by reduction of the opposite outerflat surfaces thereof on its sections adjacent to the inside cylindricalsurface of the blank to a value not greater than half of the width ofthe ring blank in the section diametrically opposite to the split of thering blank and Compression is gradually decreased along an arc 180* to aminimum value at the ends of the blank in the place of the split, heattreating the blank for imparting a homogeneous structure to the materialthereof and consecutively machining the blank on its outer flat surfacesand inside and outside cylindrical surfaces to a preset size.